1. Field of the Invention
With reference to the classification of art as established in the United States Patent and Trademark Office the present invention is found in the general Class entitled, "Classifying, Separating and Assorting Solids" (Class 209) and in the subclass entitled, "sifting-attaching perforated sheet" (subclass 399).
2. Description of the Prior Art
Shaker screens for sifting sand, rock and the like are well known and are conventionally constructed of woven screen or perforated metal. One of the problems encountered in the use of such a shaker screen is the replacement of the screen portion when it is damaged or worn out through the abrasive action of the material which is being sifted. It is well known to retain these screens by means of screws mounted in appropriately threaded portions of the frame but insofar as is known a ready replacement mechanism whereby these screen may be readily lifted from the frame and replaced in the matter of a minute or two has not heretofore been accomplished.
Examples of various patents directed toward the securing of screens to shaker frames are shown in several United States Patents among which are: U.S. Pat. No. 656,098 to M. R. DRISCOLL as issued on Aug. 14, 1900; U.S. Pat. No. 981,249 to L. A. DIETRICK as issued on Jan. 10, 1911; U.S. Pat. No. 1,353,545 to T. J. STURTEVANT as issued on Sept. 21, 1920; U.S. Pat. No. 1,545,679 to L. L. MILLER as issued on July 14, 1925; U.S. Pat. No. 1,711,548 to L. E. SOLDAN as issued on May 7, 1929; U.S. Pat. No. 2,114,329 to D. M. BLACKBURN as issued on Apr. 19, 1938 and U.S. Pat. No. 2,706,932 to R. E. SMITH as issued on Apr. 26, 1955.
In these and the other apparatus that are known the attachment of the screen is a slow and tedious project whereas in the present invention the replacement of the screen is easily accomplished and the retaining of the screen is virtually foolproof.